In many wireless communication networks, there are areas that are not easily covered by access points due to signal attenuation by terrain or other structural obstacles. One approach to extending access point signal coverage involves using relay nodes that rebroadcast signals originating from and/or destined to access points.
One major roadblock to successful implementation of relays is the problem of self-interference; relays may suffer from issues resulting from cross-talk between transmitters and receivers, duplexer leakages, or other undesired electromagnetic couplings. Many modern relays use frequency or time division multiplexing techniques or antenna separation techniques to address self-interference. Each of these techniques has substantial drawbacks: frequency division multiplexing requires doubling spectrum usage, time division multiplexing requires halving signal capacity, and antenna separation is often expensive, if not impossible given space constraints. Full-duplex relays may address self-interference without any of these drawbacks. Full-duplex communication technology may find use not only in relays, but also in a wide variety of communications applications.
In all of these full-duplex applications circuit design choices must be made. While traditional analog electronics and digital electronics are common choices for such circuits, in some cases, the drawbacks of these technologies (e.g., loss, size, cost, bandwidth) may prove prohibitive. Photonic, optoelectronic, opto-acoustic, and/or optomechanical circuits may address these concerns. Thus, there is a need in the wireless communications field to create new and useful systems for optically enhanced self-interference cancellation. This invention provides such new and useful systems.